Del Potro takes Isner down in heavyweight battle at US Open

Juan Martin del Potro has looked unstoppable in New York so far. (Getty Images)

NEW YORK (AP) — The Latest on the U.S. Open tennis tournament (all times local):

2:05 a.m.

Defending champion Rafael Nadal shockingly was shut out in the first set of his U.S. Open quarterfinal before coming back to beat No. 9 seed Dominic Thiem 0-6, 6-4, 7-5, 6-7 (4), 7-6 (5) in 4 hours, 49 minutes.

It was only the fourth time in 282 career Grand Slam matches that Nadal lost a set by a 6-0 score. It's the first time he won the match after that kind of start.

This one was never easy: Nadal trailed by a break in the third set before taking it. He came within two points of victory late in the fourth set before being pushed to a fifth, where he was two points from a loss.

But Nadal held on and is into the semifinals at a third consecutive major tournament as he bids for a fourth U.S. Open title and 18th Grand Slam trophy overall.

Defending champion Rafael Nadal and Dominic Thiem are heading to a fifth set in their U.S. Open quarterfinal.

Nadal was shockingly shut out in the first set by a 6-0 score, before coming back to take the next two 6-4, 7-5. But after Nadal came within two points of victory, Thiem wound up taking the fourth set 7-6 (4).

This is a rematch of the French Open final, won by Nadal in June.

Nadal is bidding for a fourth U.S. Open title and 18th Grand Slam trophy overall. Thiem has never won a major tournament.

The winner of this match faces 2009 champion Juan Martin del Potro in the semifinals.

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8:50 p.m.

Serena Williams shook off a slow start to grab eight consecutive games and beat 2016 runner-up Karolina Pliskova 6-4, 6-3 for a spot in the U.S. Open semifinals.

Williams delivered 13 aces, part of a 35-12 edge in winners.

But she trailed by a break in the opening set, and then was a point from being behind 4-1, before turning things around.

Williams reached her 36th Grand Slam semifinal and her 12th at Flushing Meadows, where she is a six-time champion.

Pliskova is the last woman to beat Williams at the U.S. Open, eliminating her in the semifinals two years ago. Williams missed the U.S. Open a year ago because she gave birth to her daughter during the tournament.

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5:35 p.m.

Juan Martin del Potro beat John Isner to make a second straight U.S. Open semifinal, and extend the Americans' drought at their host tournament.

The 2009 champion won 6-7 (5), 6-3, 7-6 (4), 6-2 and will face top-ranked Rafael Nadal or No. 9 Dominic Thiem in the semifinals. Nadal beat del Potro last year in the semifinals at Flushing Meadows, and again this year in the semifinals of the French Open.

Isner was trying to become the first American man to reach the U.S. Open semifinals since Andy Roddick in 2006.

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1:50 p.m.

As one American star lost in the main draw Tuesday, another of the country's rising stars was on display at the U.S. Open.

Top-seeded junior Cori "Coco" Gauff won her second round match in straight sets, 6-2, 6-2, over Romanian Selma Stefania Cadar, before juniors matches were suspended because of the heat.

The 14-year-old comes into this tournament as the second-ranked junior in the world after winning the girls' French Open title earlier this year. She received a wild card into last year's U.S. Open and became the youngest player ever to make the girls' final.

Gauff's father, Corey, played basketball at Georgia State and her mother, Candi, ran track at Florida State.

Gauff said she tried both those sports, but found her niche with tennis.

Gauff received a wild card this year into the qualifiers for the main draw at Flushing Meadows, but lost 6-4, 6-1 to Heather Watson of England.

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1:40 p.m.

Defending champion Sloane Stephens has been knocked out of the U.S. Open in straight sets.

Anastasija Sevastova, the No. 19 seed, dominated Stephens 6-2, 6-3 to reach her first semifinal in Flushing Meadows after making it to the quarterfinals the past two years.

Stephens beat Sevastova a year ago on her way to the title, but had no answer for the Latvian on Tuesday.

Sevastova came into the match having broken her opponent's serve a tournament-leading 23 times. She broke Stephens twice in the opening set, including at love in the final game.

She broke again to go up 2-0 in the second set before Stephens, pleading with herself to fight, broke back.

But Sevastova broke again to go up 3-1.

She then dropped her racket and held her hands to her face as a Stephens shot went into the net on the match's final point.

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11:45 a.m.

The extreme heat policy is in effect for a second consecutive day at the U.S. Open.

A 10-minute break will be allowed between the second and third sets of women's singles matches if either player requests one. For men's singles matches, the break would come between the third and fourth sets.

The policy is a rule on the women's tour but not the men's. U.S. Open officials began putting it in play last week, when temperatures first soared into the mid-90s. The policy was in place Tuesday through Thursday.

It was 86 degrees just before the start of Tuesday's quarterfinal between Anastasija Sevastova and defending champion Sloane Stevens on Arthur Ashe Stadium, with temperatures again expected to rise through the 90s.

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11:30 a.m.

Serena Williams and Sloane Stephens can give the United States two U.S. Open semifinalists, a year after an all-American women's final four.

And for the first time since 2006, the host country can have a man there, too.

Williams and Stephens first have to win quarterfinal matches Tuesday. Defending champion Stephens is up first on Arthur Ashe Stadium, facing No. 19 seed Anastasija Sevastova in a rematch of Stephens' three-set victory in the same round at Flushing Meadows last year.

Williams, seeded 17th, meets the last player to beat her at the U.S. Open. Karolina Pliskova, the No. 8 seed, knocked off Williams in the 2016 semifinals before the 23-time Grand Slam champion missed last year's tournament, when she gave birth.

On the men's side, defending champion Rafael Nadal faces Dominic Thiem at night in a rematch of Nadal's French Open victory, and 2009 U.S. Open champion Juan Martin del Potro plays John Isner in the other quarterfinal.

If Isner wins, he would be the first American in the U.S. Open semifinals since Andy Roddick in 2006.